Solar energy was orignally commonly obtained from uni-solar thin film flexible solar PV panels, but a more cost-efficient method is on the rise. From the start, the uni-solar models were popular because of their price, but due to increasing prices of polysilicon, this method is being abandoned. Early applications demonstrated the need for thin-film PV panels, for uses such as landfills and metal roofs, because traditional solar panels were impractical here. While there is still a need for these thin-film sheets, they have yet to be developed to survive in a competitive environment at a cheaper price.

Hanergy, a Chinese conglomerate, is the lead producer specializing in thin film manufacturing. Hanergy believes that thin-film and flexibility will define the future of the PV industry. The weight of the thin film produced by MiaSole, a division of Hanergy here in the United States, is 0.6 lbs/sq ft. This is an advanced CIGS (copper-Indium-Gallium-Selenide) technology and has about 16% efficiency.

Until now, the promise of 'zero-energy' buildings has been held back by two main obstacles: the cost of the thin-film solar cells and the fact they're constructed from scarce, and highly toxic, materials.

The University of New South Wales is working to overcome these obstacles. A group at the university, led by Dr. Xiaojing Hao of the Australian Centre for Advanced Photovoltaics at the UNSW School of Photovoltaic and Renewable Energy Engineering, has achieved the world's highest efficiency rating for a full-sized thin-film solar cell using a competing thin-film technology, known as CZTS.Unlike its thin-film competitors, CZTS cells are made from abundant materials: copper, zinc, tin and sulphur. Hao's team believes thin-film photovoltaic cells that can be rigid or flexible, and durable and cheap enough to be widely integrated into buildings to generate electricity from the sunlight that strikes structures such as glazing, façades, roof tiles and windows. "This is the first step on CZTS's road to beyond 20% efficiency, and marks a milestone in its journey from the lab to commercial product," said Hao. "There is still a lot of work needed to catch up with CdTe and CIGS, in both efficiency and cell size, but we are well on the way.".

However, because CZTS is cheaper and easier to bring from lab to commercialization than other thin-film solar cells, it is likely that applications are near term. University of South Wales is collaborating with a number of large companies keen to develop these panels well before the technology reaches 20% efficiency goal, Hao says, within the next few years.